The preferred embodiment of the invention includes attachment and interconnection methods which are described below in the context of a field emission flat-panel display. Such a flat-panel display is also described in two concurrently-filed applications, both assigned to Micron Display Technology, Inc., entitled "Internal Plate Flat-Panel Field Emission Display" and "Multi-Layer Electrical Interconnection Structures and Fabrication Methods," the disclosures of which are hereby incorporated by reference. The methods described and claimed herein are particularly useful in conjunction with a flat-panel display. They will also find advantageous application in the context of other circuits in which a first substrate is to be mounted face down for electrical connection between facing bond pads of the first substrate and of an underlying second substrate.
This type of connection is commonly made with flip-chip technology or bonding. Flip-chip technology forms conductive bonds between facing conductors of adjacent planar substrates. These bonds are typically formed with a small conductive "bump" which is compressed between the facing conductors, often in the presence of applied heat. Such bumps have in the past been formed with specialized equipment. More recently, they have been formed with conventional wire bonding equipment by placing a single bonding wire ball or "ball bond" on one of the surfaces which is to be bonded. This ball is subsequently compressed between conductors to form a conductive bond therebetween.
While existing flip-chip technology is useful in many situations, the techniques described above are limited to a narrow range of bumping materials. For instance, it is difficult create ball bonds with aluminum bonding wire. In contrast, the invention described and claimed below allows the use of a wide range of materials for formation of flip-chip bonds.